1. Field of the Invention
The present invention relates to a method and an apparatus for driving a selvedge forming device of the tuck-in type capable of cutting a weft beaten by a reed and tucking the end portion of the cut weft in a warp shed.
2. Prior Art
There has been proposed a tuck-in type selvedge forming technique of this kind which uses a cutter for cutting a weft inserted by weft insertion, a weft holding device for holding the end portion of the cut weft by means of an air stream, and a tuck-in needle for use in tucking the end portion of the cut weft in a warp shed (see Japanese Patent Application Public Disclosure (KOKAI) No. 62-53450). In this prior art, each of the selvedge forming parts (selvedge forming elements) contributing to the selvedge formation, for instance, a cutter, a weft holder, a tuck-in needle, and so forth are respectively operated at a predetermined constant timing. If the type of weft is changed, the air supply pressure is regulated so as to meet this weft change.
Furthermore, there has been proposed another tuck-in type selvedge forming technique which uses an electromagnetic actuator for operating at least one of the selvedge forming elements including a weft holding device, a cutter and parts as used for tuck-in operation, and an operating instruction device for outputting a signal for keeping the electromagnetic actuator in the operable or inoperable state according to a pile weaving signal from a weaving pattern control device of the weaving machine and a rotational angle signal which is the rotational angle of the main shaft of the weaving machine (see Japanese Patent Application Public Disclosure (KOKAI) No. 2-112446). In this prior art, during the pile weaving process, the selvedge forming elements are operated only in a pile weaving cycle next to the preceding one, whereby a plurality of wefts inserted by weft insertion while the selvedge forming elements are in the inoperable state are tucked in all together, and the selvedge forming elements are operated every weft insertion during the non-pile weaving process forming no pile, whereby wefts are tucked in on a weft-by-weft basis.
There has been proposed still another tuck-in type selvedge forming technique wherein, during the pile weaving process, a plurality of wefts are tucked in all together in the pile weaving cycle next to the preceding one, and during the non-pile weaving process forming no pile, the weft is tucked in every weft insertion (see Japanese Patent No. 2,501,845). In this prior art, the driving of the selvedge forming elements is stopped in correspondence to the weaving structure, that is, the weaving condition.
In all cases of the prior art as described above, however, the operating condition (tuck-in condition) for actually operating the selvedge forming elements is not only unchanged in the process of tucking the weft in the warp shed, but also unchanged even if the weaving condition is switched. Like this, in the prior art as described above, the condition for actually operating the selvedge forming elements is unchanged even though the weaving condition is switched, so that it possibly occurs that some selvedge structures are formed under an inappropriate operating condition, thus coming to form a selvedge structure lacking in uniformity.
Especially, in cases of high value added fabrics, they have to be woven by taking into account various factors and operating conditions, for instance the type of weft [as] used, a position of the cloth fell (influenced by the weft (pick) density, the fabric structure, the circumstances of the warp shed, etc.), the rotational speed (or number) of the weaving machine and so forth. In addition to these, the high value added fabric has to be woven by changing the weaving condition such as the operation or non-operation of the selvedge forming elements, in accordance with the weaving pattern. Accordingly, it is hardly possible for the prior art as described above to provide the high value added fabric having a uniform selvedge structure.
In the case of a selvedge forming device of the type wherein fluid like air or water is used for holding the weft or tucking the weft end portion in the warp shed, the excess and insufficiency in the operating condition with respect to the weft end portion to be tucked in the warp shed has a great influence on formation of the selvedge structure. For instance, insufficient air jetting results in tuck-in failure caused by incomplete tuck-in operation, while excessive air jetting possibly damages the weft and/or the warp forming the warp shed, thus resulting in fabric defect in either case.
Accordingly, what is important is to form a uniform tuck-in type selvedge structure without being influenced by switching of the weaving condition.